Agricultural working machines generally comprise elements that can be adjusted, i.e. displaced linearly, or pivoted relative to the working machine, by associated actuators. In the case of a tractor, such elements include implements attached to the front or rear power lifts for cultivation, sowing or for applying fertilizer or other chemicals; for a self-propelled field sprayer, they include a sprayer boom that is height-adjustable and/or pivotable about an axis extending in the forward direction; for a combine or forage harvester, they include a harvester head that is pivotable about a horizontal axis oriented transversely to the forward direction (generally the axis of rotation of the upper inclined conveyor roller or chopper drum) and/or pivotable about an axis extending in the forward direction for parallel orientation on a slope, or an ejection pipe of a forage harvester that is height-adjustable in order to adjust the height of its outlet pipe and/or is height-adjustable about the vertical axis. The target position of the actuator and thus of the adjustable element is specified by a user via a suitable interface or by an automatic controller interacting with sensors.
Because the working machine rests on wheels filled with air (and are thus resiliently yielding) and can also be furnished with a suspension between the wheels and the body of the working machine, the system consisting of the adjustable element and the working machine is stimulated into (natural) oscillation, which can have a disturbing effect in operation. Thus cutters can have a width of 12 m or more, and if they are guided a few centimeters above the ground, it is occasionally possible that a desired cutting height cannot be maintained due to the vibration resulting from the height adjustment.
In the prior art, control circuits are known which are equipped with a sensor for detecting the respective position of the adjustable element, the signal of which is used for feeding back the actual position of the element to a control circuit (cf. US 2009/0277145 A1, for example). In that way, any deviations from the target position caused by the vibration of the element that may occur are detected and are fed back to the control circuit, but are only damped relatively slowly.
It has also been proposed to detect possible causes, e.g. ground unevenness, for vibrations of an implement attached to an agricultural vehicle and to identify their influence on the attached implement in order to trigger the actuator to act in opposite phase to the expected cause of vibrations and thus avoid an undesired vibration of the element (DE 34 46 811 C2, DE 10 2010 017 459 A1). This procedure does not take vibrations resulting from changing the target position of the element into account and can therefore not counteract such vibrations.